Theoretical analysis of a realistic atom-chip quantum gate (9 pages)

Jonathan A. Jones, Xiao Liang

M. A. Cirone, Antonio Negretti, Tommaso Calarco +2 more

Zhongxiang Han, Yun‐Feng Xiao, Guang‐Can Guo

Matthias M. Müller, Harald R. Haakh, Tommaso Calarco +2 more

Éric Charron, M. A. Cirone, Antonio Negretti +2 more

We present a detailed, realistic analysis of the implementation of a proposal for a quantum phase gate based on atomic vibrational states, specializing it to neutral rubidium atoms on atom chips. We show how to create a double-well potential with static currents on the atom chips, using for all relevant parameters values that are achieved with present technology. The potential barrier between the two wells can be modified by varying the currents in order to realize a quantum phase gate for qubit states encoded in the atomic external degree of freedom. The gate performance is analyzed through numerical simulations; the operation time is $\ensuremath{\sim}10\phantom{\rule{0.3em}{0ex}}\mathrm{ms}$ with a performance fidelity above 99.9%. For storage of the state between the operations the qubit state can be transferred efficiently via Raman transitions to two hyperfine states, where its decoherence is strongly inhibited. In addition we discuss the limits imposed by the proximity of the surface to the gate fidelity.

Philipp Treutlein, Theodor W. Hänsch, Jakob Reichel +3 more

We propose a two-qubit collisional phase gate that can be implemented with available atom chip technology and present a detailed theoretical analysis of its performance. The gate is based on earlier phase gate schemes, but uses a qubit state pair with an experimentally demonstrated, very long coherence lifetime. Microwave near fields play a key role in our implementation as a means to realize the state-dependent potentials required for conditional dynamics. Quantum control algorithms are used to optimize gate performance. We employ circuit configurations that can be built with current fabrication processes and extensively discuss the impact of technical noise and imperfections that characterize an actual atom chip. We find an overall infidelity compatible with requirements for fault-tolerant quantum computation.